Rheostat mechanism



Aug. 8, 1950 P. H. vooRLAs RHEOSTAT MECHANISM Filed aan. 2v, 1949 FIGA INVENTOR. FFS-ITER H., VORLAE AT T R N Patented Aug. 8, 1950 UNITED STATES PATE/NT OFFICE 2,517,614 RHEOSTAT MECEANISPJI Peter H. Voorlas, Racine, Wis.

Application January 27, 1949, Serial lilo. 13,037 cia-rms. (c1. zei-i3) This invention relates to controllable resistors for electric circuits.

It is an object of my invention to provide a novel and improved highly eicient controllable electric resistor having a particularly eii'icient body construction designed to permit quick and easy construction of a rheostat unit.

It is another object to provide a particularly eii'cient insulator body construction for a controllable electric resistor whereby Winding of the resistor to produce equal resistance between the stationary contacts thereof is greatly facilitated.

It is a further object to provide a simple connection member which is adapted to permit a positive electric connection to be made between intermediate portions of the resistance winding of an electric resistor and the stationary contact of the resistor during the winding operation without interruption of said winding operation.

More specifically, it is an object to provide a rheostat having a flat generally T-shaped body with a continuous spiral groove formed in the cross member of the T and having a plurality of spaced stationary contact elements extending respectively downwardly into adjacent portions of the spiral groove, each with a connector element adapted to receive the resistor Wire and make contact therewith during the course of the normal winding operation, and the outstanding stein of the T being adapted to pivotally receive a movable contact arm for swingably traversing said cross member to selectively contact the stationary contact elements.

It is still a further object to provide an extremely efcient and commercially successful method whereby a continuous integral winding of resistance wire in the spiral groove of said body is greatly facilitated, and the individual convolutions of the wire are electrically connected to the stationary contacts simultaneously with the continuous uninterrupted winding of said wire on said body.

These and other objects and advantages of my invention will more fully appear from the following description made in connection with the accompanying drawings wherein like reference characters refer to similar parts throughout the several views and in which;

Fig. 1 is a top plan view of the resistor unit with a portion of the movable contact arm cut away;

Fig. 2 is a fragmentary transverse vertical sectional view taken substantially along the line Fig. 3 is an enlarged detail sectional VView show- 2 ingd the construction of the connector elements; an

Fig. 4 is a fragmentary longitudinal sectional View enlarged to show the construction and connection of the connector elements with the coils of resistor wire.

As illustrated in the accompanying drawings, I provide a resistor-carrying body designated as an entirety by the letter A and being generally T-shaped as viewed from the top. In the form shown the cross on the T follows a substantially circular arc, and the stem of the T divides the cross portion thereof into two substantially equal sections. A spiral groove 1 is formed in the cross portion of the body A and extends substantially the full length thereof. A plurality of stationary contacts 8 are mounted in the cross portion of the body A along the outer edge portion thereof and are circumferentially spaced along a circle having as a center the pivot point 9. The spiral groove 'I has the same general pitch throughout its length, and therefore, if the depth of the groove remained constant, the length of the in- 'dividual convolutions thereof would increase at one end due tothe generally arcuate shape of the cross portion of the T-shaped body A. Therefore,

it is necessary to vary the depth of the groove in order to control the length of the increments of the resistor member between the respective stationary contacts 8. In the form shown a spirally coiled resistor member I0 is illustrated, and the groove l is designed to permit an equal length of the wire IU to be disposed between each of the stationary contacts 8 to permit uniform variation in the current ilow to be maintained through the operation of the rheostat as will be described subsequently. The two ends of the resistor wire I0 are respectively secured to the body A as by the anchors I I and I2 which are made from any suitable electrical conductive material and are electrically connected respectively to the contacts I3 and I4. An extremely simple connector element I5 electrically interconnects the stationary vcontacts v8 with the respectively adjacent `portions of the resistor `wire I0. Said connector is generally U-shaped at one end to conform to vthecross sec- .tion -of groove 1 and has an outstanding attachment flange I6 which is connected to the respective stationary contact 8 and is securely anchored "to the vbody A thereby. The extreme bottom of the U-shaped portion of connector element I5 has-a fastening hook I 1 adapted to receive acoil of lthe resistor wire VIII land `to securely connect the same to theelement I5 and form an electric A in the groove .1. continuous, and as it proceeds, the respective conconnection between the respective stationary contact 8 and the coil of resistor wire I0. Since the tension in the resistor wire Ill will hold the engaged convolution in securely seated position at the closed end of the hook I'I, is is not necessary to crimp the hook down onto the coil; however, this may be done if desired. Fig. 4 best shows a typical connection between the hook and the engaged coil of resistor wire.

A movable contact arm I8 is pivoted on pivot point 9, and the outer end portion thereof is adapted to resiliently engage the contacts 8 to make electrical connection between the respective contact and the pivot point 9. A connection bar I9 electrically interconnects pivot point 9 with a terminal 20 mounted in one end portion of body A, and a relatively short connection bar 2I electrically interconnects contact I4 and a second terminal 22 mounted in said body A. A suitable shiftable arm operating link 23 is pivotally mounted in an intermediate portion of shiftable contact arm I3 and is connected to suitable 0D- erating mechanism (not shown) for swinging said contact arm I8 controllably through an arcuate path to selectively engage the contacts 8. A pair of stop elements 24 and 25 at the respective end portions of the cross portion of the T-shaped body Arlimit the swinging movement of the arm I8, and a pair of apertures 26 and 2l with suitable countersunk upper portions are provided to permit attachment of said body A to a suitable housing (not shown). The body A is, of course, made from any suitable rigid dielectric material or conductive material provided with dielectric resistor element receiving medium.

Due to the particularly ingenious construction of the resistor body A and connector elements I5, the method of winding the resistor element on the rheostat body is greatly simplified, The connector elements are initially mounted in the re-` spective portions of the grooves and are secured therein by the contact elements 8 to which they are respectively electrically connected. One end of the resistor wire IU is then secured to the contact I4 by the anchor member I2, and the wire is wound on the cross portion of the T-shaped body This winding operation is volutions of the spirally coiled resistor wire I adjacent attachment hooks I'I slide thereunder Y and positively engage the same without interrupting the` winding. This permits a novel highly efcient method ,of winding the resistor wire on the body A to'be used.

If it is desired to produce an equal increment I of resistance between the stationary contacts, the

depth of the groove I must be varied to permit an equal length of resistor wire to be disposed between adjacent stationary contacts to permit uniform variance of the current ow through the circuit intowhich the resistor unit is connected. It is relatively easy to wind a coiled resistor wire on v'the body A and maintain an equal tension therein during the winding operation.

It will be seen that I have provided an extremely simple, highly elicient rheostat in which the connector elements I with hook I1 combine with the shape and construction of the T-shaped body A with the groove 'i formed therein to permit an extremely easy method of winding the rheostat.

The design of my complete resistor unit is particularly adapted to modern methods of manufacture and is also adapted to compactly Iit within a' control casing and be operated bya :simple control mechanism thereof.

It will, of course, be understood that various changes may be made in the form, details, arrangement and proportions of the.parts without departing from the scope of my invention.

What I claim is:

1. A rheostat comprising a resistance-carrying body having a spiral groove formed therein, a plurality of spaced stationary contacts mounted on said body, a shiftable contact member pivoted on said body with its pivot point disposed in spaced relation to the stationary contacts and adapted to selectively engage the same, a plurality of connection elements respectively secured to said stationary contacts, each having a portion thereof disposed in adjacent portions of said groove, a resistor element wound in said groove, an attachment element mounted on each of said connection elements to electrically connect each of said stationary contacts to respectively adjacent portions of said resistor element, and means for connecting said rheostat in series into an electrical circuit to permit control of the current owing through said circuit.

2. A rheostat comprising a resistance-carrying body with a generally arcuate portion having a spiral groove formed therein, a plurality of peripherally spaced stationary contacts mounted along a circular arc having a radius substantially equal to the outer radius of the arc of said body portion, the depth of said spiral groove being varied to provide an equal increment of groove between each of said stationary contacts, a plurality of connection elements respectively secured to said stationary contacts with a portion thereof disposed in respectively adjacent portions of said groove, a resistor element wound in said groove and electrically connected to each of said stationary contacts with equal increments of resistance between each of said contacts, a shiftable contact member pivoted on said body with its pivot point disposed at the center of the circular arc described by said stationary contacts and adapted to selectively engage the same, and means for connecting said rheostat in series into an electrical circuit to permit control of the current owing through said circuit.

3. A rheostat comprising a resistance-carrying body having aspiral groove formed therein, a plurality of spaced stationary contacts mounted on said body, a shiftable contact member mounted on said body to selectively engage said contacts, a plurality of connection elements electrically connected to said stationary contacts and each having a portion thereof disposed in adjacent portions of said groove, an upstandingclip element electrically connected to each of said connection elements, a resistor element wound in said groove to positively engagesaid clip elements and form an electrical connection therewith, the tension in said resistor element holding the same in engagement with said clip elements, and means for connecting said rheostat in series into an electrical circuit to permit control of the current owing through said circuit.

4. A rheostat comprising a substantially T- shaped resistance-carrying body, the cross portion of the T being arcuately curved and having a spiral groove formed therein, a plurality of peripherally spaced stationary contacts mounted on said body along a circular arc concentrically disposed relative to the arc of said body portion, an electrically conductive shiftable contact member pivoted on the stem'of said body with its pivot pOint disposed substantially at the center of rsaid circular arcs and adapted to selectively necting said rheostat in series into an electrical 5 circuit to permit control of the current ilowing through said circuit.

5. The method of winding a resistance element on a body having spiral grooves formed therein and provided with a plurality of connection elements having upstanding attachment clips mounted in said groove, said method consisting in continuously winding a spirally coiled resistance element in said groove, engaging certain convolutions of said resistance element under said 15 upstanding clip elements during the continuous winding operation to form a positive electrical connection therewith and prevent interruption of the Winding operation.

PETER H. VOORLAS.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS 10 Number Name Date 1,142,586 Law l June 8, 1915 1,351,023 Chantemerle Aug. 31, 1920 FOREIGN PATENTS Number Country Date 172,115 Canada Sept. 26, 1916 236,248 Great Britain June 29, 1925 

